Vehicle radiators of the parallel flow type comprise a metal core, consisting of brazed flow tubes and cooling fins, flanked by a pair of manifold tanks that feed coolant into and out of the core. The outlet tank, which receives the coolant after it has been cooled in the core, has a lower temperature than the inlet tank, and is the logical candidate for the inclusion of independent, auxiliary heat exchangers used to cool transmission fluid or lubricant oil. These are generally referred to just as oil coolers. Oil runs through the oil cooler, sealed off from the radiator coolant, but bathed in and cooled by it. The manifold tanks, increasingly, are molded plastic units, and can be made with a volume adequate to enclose the additional oil cooler without a great increase in weight, beyond the inevitable weight of the oil cooler itself. The plastic manifold tank is typically molded with a pair of through holes in one side wall to accommodate the inlet and outlet of the oil cooler. A good example of this type of radiator and cooler may be seen in co assigned U.S. Pat. No. 5,067,561 issued Nov. 26, 1991 to Joshi et al., and is described in further detail below.
Another trend in automotive design is the accommodation of as many build variations as possible with only a few standard or modular components. Vehicles in one model line will likely be built with or without an oil cooler, depending on the engine and transmission package selected. The radiator should be capable of selectively incorporating the oil cooler, or not, as needed, with as little change as possible. If the oil cooler is not to be installed, then the radiator outlet tank mold is modified to seal off the through holes and make the tank wall integral at that point, or they are otherwise plugged. The radiator operates just as before. However, there is an inevitable increase in the volume (and weight) of coolant in the outlet tank, as coolant now fills the void left by the missing oil cooler. This can add nearly as much weight as the oil cooler itself, and vehicle weight reduction is a continual concern.